This invention relates generally to flash fusing and more specifically to improved toner compositions for use in flash fusing electrographic imaging processes.
In the electrophotographic process and more specifically the xerographic process, a plate generally comprising a conductive backing upon which is placed a photoconductive insulating surface is uniformly charged and subsequently the photoconductive surface is exposed to a light image of the original to be reproduced. The photoconductive surface is made in such a manner so as to cause it to become conductive under the influence of the light image in order that the electrostatic charge found thereon can be selectively dissipated to produce what is developed by means of a variety of pigmented resin materials specifically made for this purpose, such as toners. The toner material used is electrostatically attracted to the latent image areas on the plate in proportion to the charge concentration contained thereon. For example, areas of high charge of concentration become areas of high toner density and correspondingly low charge images become proportionately less dense. Subsequently, the developed image is transferred to a final support material such as paper and fixed thereto for a permanent record or copy of the original.
Many methods are known for applying the electroscopic particles to the electrostatic latent image to be developed such as for example the development method described in E. N. Wise U.S. Pat. No. 2,618,552, "Cascade Development." Another method of developing electrostatic latent images is in the magnetic brush process as disclosed for example in U.S. Pat. Nos. 2,874,063; 3,251,706; and 3,357,402. In this method a developer material containing toner and magnetic carrier particles is carried by a magnet with the magnetic field of the magnet causing alignment of the magnetic carrier into a brush like configuration. The magnetic brush is brought in close proximity of the electrostatic latent image bearing surface and the toner particles are drawn from the brush to the electrostatic latent image by electrostatic attraction. Other methods of development include for example powder cloud development as described in C. F. Carlson U.S. Pat. No. 2,221,776, touchdown development as described in R. W. Gundlach U.S. Pat. No. 3,166,432 and cascade development as described in U.S. Pat. No. 3,099,943.
Fixing of the image can be accomplished in a number of various techniques including for example those that are more commonly used such as vapor fixing, heat fixing, pressure fixing, or combinations thereof as described for example in U.S. Pat. No. 3,539,161. These techniques of fixing do suffer from some deficiencies which render their use either impractical or difficult for specific electrostatographic applications. For example, it has been found rather difficult to construct an entirely satisfactory heat fuser which has short warm up time, high efficiency and ease of control. Another problem generally associated with heat fusers is that they burn or scorch the support material, for example, paper. Similar problems exist with pressure fixing methods whether used with heat or without heat and more particularly such problems include for example image offsetting, resolution degradation, and further there cannot be consistently produced a good permanent type of fix. Vapor fixing has many advantages but it has one overriding problem in that a toxic solvent has to be used which in most cases make it commercially inoperable because of the health hazards and pollution control standards involved. For example, equipment and apparatus to sufficiently isolate the fuser from the surrounding air must be by its very nature very complex, costly, difficult to operate, and difficult to contain consistent results.
Modern electrostatographic reproducing apparatus resulted in the development of new materials and new processing techniques, one main development being the production of an automatic electrostatographic reproducing apparatus which is capable of producing copies at extremely rapid rates. It has been found that the best method for fixing in such types of machine is radiant flash fusing. One of the main advantages of the flash fuser over other known methods is that the energy which is emitted in the form of electromagnetic waves is instantly available and requires no intervening medium for its propagation. However, although an extremely rapid transfer of energy between the source and the receiving body is provided when using the flash fusing process, one major problem encountered with such a system is designing an apparatus which can fully and efficiently utilize a preponderance of the radiant energy emitted by the source during a relatively short flash period. The toner image usually comprises a relatively small percentage of the total area of the copy receiving the radiant energy and because of the properties of most copying materials, as for example, paper, most of the energy thereon is wasted by being transmitted through the copy or being reflected away from the fusing area.
Additionally, when radiant energy from a flash fuser is generated at levels necessary to fuse the toner, objectional odor and smoke results in some instances because of the thermal decomposition of the base resin at the temperature at which fusing must occur.